Photoelectric and magnetic properties of Fe-hyperdoped Si layers formed by the recoil-atom implantation

Abstract

The doping of near-surface region of single crystalline p-type Si by Fe impurity under irradiation by the low-energy and high-current Xe+ ion beam is investigated. The recoil-atom implantation method was applied which utilizes simultaneous sputtering of Fe target with irradiation of the deposited Fe atoms on the Si substrate surface by Xe+ ion beam. The resulting incorporation of Fe atoms into Si leads to formation of very thin (~5 nm) highly doped (>1022 at/cm3) surface layer (Si:Fe) containing Si and α-Fe nanoparticles with sizes of 5–20 nm. Such a layer demonstrates ferromagnetism at T = 10 K and superparamagnetism at 300 K. Inversion of the conductivity type (from p-to n-type) in the heavily doped Si:Fe layer and formation of n-p junction to the substrate is observed. A photoresponse of thus obtained n-Si:Fe/p-Si diode structure demonstrates an intense signal in the wavelength range of 500–1200 nm with a maximum at about 950 nm under the low reverse bias voltage (U = 1 V), whose integral intensity is comparable with that for commercial silicon photodiode at U = 10 V.